Groundwater supply is subjected to groundwater flow and contamination due to migration of pollutant in the aquifer systems. It is essential to investigate the quantity and quality of single aquifer or multi-layer aquifer for groundwater management. Many researchers have explored the problem of transient well flow in multi-layer aquifer associated with pollutant transport in subsurface systems. However, the nature of the physical process generates complexity in theoretical formulation. Hence, it is recognized that realistic solutions may only be determined by utilizing numerical approximation techniques. The primary objective of this research is to develop and validate a numerical model in order to analyze groundwater flow and pollutant transport problem into a well in an unconfined-confined aquifer system. The model is intended for assessing the performance of groundwater flow into a well when it is pumped from either unconfined or unconfined-confined aquifer. The model is also to study the pollutant transport occurrence during the pumping operation under saturated condition of the unconfined aquifer system. This study proposes numerical model for the groundwater flow into a well in fully coupled unconfined-confined aquifer system, which considers advection and dispersion processes of pollutant transport. The mathematical governing equations are second order partial differential equations that have been solved numerically using a finite difference method. A computer program written using MATLAB is developed to solve these equations. Three separate programs are developed in this study. The first one is quite generic and is used to simulate groundwater flow into a well in an unconfined-confined aquifer. The other two are more specific and are used to predict the pollutant transport problem in an unconfined aquifer for one- and two-dimensional flow respectively. The solution method reduces the complexity of theoretical formulation in multi-layer aquifer, and the numerical model is validated using experimental data, available analytical solution and field data. The experimental data obtained from laboratory model and the field data are collected from the Surabaya aquifer, East Java, Indonesia. It was discovered that the two-dimensional flow model could predict the magnitude of the flow at an acceptable sensitivity. In the case of pollutant transport problem, the one- and two-dimensional models showed good performance. The horizontal spreading of the contaminant was more obvious when the water was tapped from the unconfined aquifer. The proposed numerical models are also capable of simulating a big scale problem.
DWI TJAHJANTO; Faculty of Civil Engineering
DWI TJAHJANTO; Faculty of Civil Engineering
